My computer restarts only when I am encoding something..(MCE error)

Hi. Before registering I read all similiar threads regarding to my problem. I didn't solved it. So, I decided to open a new one and get help from you guys.

I bought a new processor, AMD Sempron 2800+, a new Foxconn NF3 motherboard and a 512MB DDR memory. I didn't had problems installing them, but when I started using my new machine on a new Windows my problems appeared.

My computer keeps restarting, and I don't know why! Computer restarts only when I am trying to encode some video (DVD to Divx or similiar) and I tried to encode with different tools - nah, that doesn't help - it's still restarting.

I saw that my machine is reporting BSOD with a error: MACHINE_CHECK_EXCEPTION.

I thought it was a memory but I downloaded memtest and passed 3-4 with no errors. My temperature is 40 C, so processor is not the problem. I have power supply of 400W (bought in 2006) and I didn't had any of problems with it. I am stuck here for 3 weeks and I don't know what to do. Can you help me? Here are my minidumps.

NOTE: This is a hardware error. This error was reported by the CPU
via Interrupt 18. This analysis will provide more information about
the specific error. Please contact the manufacturer for additional
information about this error and troubleshooting assistance.

VAL - MCi_STATUS register is valid
Indicates that the information contained within the IA32_MCi_STATUS
register is valid. When this flag is set, the processor follows the
rules given for the OVER flag in the IA32_MCi_STATUS register when
overwriting previously valid entries. The processor sets the VAL
flag and software is responsible for clearing it.

OVER - Error Overflow
Indicates that a machine check error occurred while the results of a
previous error were still in the error-reporting register bank (that
is, the VAL bit was already set in the IA32_MCi_STATUS register).
the processor sets the OVER flag and software is responsible for
clearing it. Enabled errors are written over disabled errors, and
uncorrected errors are written over corrected errors. Uncorrected
errors are not written over previous valid uncorrected errors.

UC - Error Uncorrected
Indicates that the processor did not or was not able to correct the
error condition. When clear, this flag indicates that the processor
was able to correct the error condition.

EN - Error Enabled
Indicates that the error was enabled by the associated EEj bit of the
IA32_MCi_CTL register.

This error code can be reported back to the manufacturer.
They may be able to provide additional information based upon
this error. All questions regarding STOP 0x9C should be
directed to the hardware manufacturer.

If you got the same error, then you should send it back and get them to look at it. You've run two CPU intensive programs (video encoding and prime95) and it's crashed with both, so I don't think there's much else you can do.